The typical film spool, such as a supply spool in a film cartridge or a take-up spool in a camera, is known to include some means for releaseably attaching a film end to the spool.
For example, prior art U.S. Pat. No. 4,334,750, issued Jun. 15, 1982, discloses a film spool comprising an off-axis peripheral slot in the spool core which is dimensioned to receive a reduced-width film end, and a film engagement protrusion that projects through an internal opening into the slot to engage the film end. The engagement protrusion is located on one of two legs of a u-shaped resilient member which is slidable inwardly along a central hollow in the spool core until the engagement protrusion pops through the internal opening from the central hollow into the slot to engage the film end. To release the film end, the engagement protrusion is retracted through the internal opening from the slot into the central hollow as a result of sliding the u-shaped resilient member further along the central hollow against a fixed camming incline in the hollow.
According to another example, prior art U.S. Pat. No. 2,917,251, issued Dec. 15, 1959, discloses a film spool comprising an intermediate resilient hollow section of the spool core which can be bulged outwardly by pressing inwardly at opposite ends of the core. As a result, a pair of axially extending peripheral slits in the spool core will be opened to permit a film end to be inserted into the slits.